Power tool with automatic feathering mode

Abstract

A power tool includes a housing, a motor disposed in the housing, an output spindle configured to be driven by the motor, an input switch, and a controller configured to control power being delivered to the motor. The controller is operable in one of: (a) a normal mode where the controller causes continuous electric power to be delivered to the motor during actuation of the input switch in a first range of positions; and (b) a feathering mode where the controller causes discontinuous electric power to be delivered to the motor during actuation of the input switch in a second range of positions that is different from the first range of positions motor to simulate feathering the input switch.

What is claimed is: 
     
       1. A method of operating a power tool coupled to a source of electric power and having a motor, a controller, and an input switch, the method comprising:
 determining, in the controller, a position of the input switch that is moveable in a first range of positions between a preset deactivated position and a first preset intermediate position and in a second range of positions between the first preset intermediate position and a preset actuated position, the first intermediate position between the deactivated position and the actuated position; 
 delivering continuous electric power to the motor when the determined position of the input switch is within the first range of positions, the continuous electric power causing continuous rotation of the motor; and 
 delivering discontinuous electric power to the motor when the determined position of the input switch is within the second range of positions, the discontinuous power causing discontinuous rotation of the motor to simulate feathering the input switch. 
 
     
     
       2. The method of  claim 1 , wherein the discontinuous electric power comprises pulses of electrical power with a frequency low enough to be perceptible to a user. 
     
     
       3. The method of  claim 2 , wherein the pulses of electric power comprise pulses of a first power interrupted by pulses of a second power that is different than the first power. 
     
     
       4. The method of  claim 1 , further comprising a second intermediate position of the input switch between the deactivated position and the actuated position, wherein the first range of positions comprises a first subrange of positions between the deactivated position and the second intermediate position and a second subrange of positions between the second intermediate position and the first intermediate position, and wherein delivering continuous electric power comprises delivering a variable amount of electric power when the input switch is within the first subrange of positions, and delivering a constant amount of electric power when the input switch is within the second subrange of positions. 
     
     
       5. The method of  claim 1 , further comprising transitioning from delivering continuous electric power to the motor to delivering discontinuous electric power to the motor, independent of an amount of current drawn by the motor. 
     
     
       6. A power tool comprising:
 a housing; 
 a motor disposed in the housing; 
 an output spindle configured to be driven by the motor; 
 an input switch moveable in a first range of positions between a preset deactivated position and a first preset intermediate position and in a second range of positions between the first preset intermediate position and a preset actuated position, the first intermediate position between the deactivated position and the actuated position; and 
 a controller configured to control power being delivered to the motor, wherein the controller is operable in one of: (a) a normal mode where the controller causes continuous electric power to be delivered to the motor during actuation of the input switch in the first range of positions; and (b) a feathering mode where the controller causes discontinuous electric power to be delivered to the motor during actuation of the input switch in the second range of positions to simulate feathering the input switch. 
 
     
     
       7. The power tool of  claim 6 , wherein the discontinuous electric power comprises pulses of electrical power with a frequency low enough to be perceptible to a user. 
     
     
       8. The power tool of  claim 6 , wherein the pulses of electric power comprise pulses of a first power interrupted by pulses of a second power that is different than the first power. 
     
     
       9. The power tool of  claim 6 , further comprising a second intermediate position of the input switch between the deactivated position and the actuated position, wherein the first range of positions comprises a first subrange of positions between the deactivated position and the second intermediate position and a second subrange of positions between the second intermediate position and the first intermediate position, and wherein delivering continuous electric power comprises delivering a variable amount of electric power when the input switch is within the first subrange of positions, and delivering a constant amount of electric power when the input switch is within the second subrange of positions. 
     
     
       10. The power tool of  claim 6 , further comprising a first biasing element that biases the input switch toward the deactivated position during actuation of the input switch in the first and second ranges of positions, and a second biasing element that engages the input switch at an intermediate position between the first range of positions and the second range of positions to provide additional biasing force against the input switch. 
     
     
       11. The power tool of  claim 10 , wherein the second biasing element comprises a biased detent that engages the input switch at the intermediate position such that additional force is needed to actuate the input switch past the intermediate position from the first range of positions to the second range of positions. 
     
     
       12. The power tool of  claim 10 , wherein the second biasing element comprises a biased lever that engages the input switch through the second range of positions such that additional force is needed to actuate the input switch in the second range of positions than in the first range of positions. 
     
     
       13. The power tool of  claim 6 , wherein the controller is operable to transition from operation in the normal mode to operation in the feathering mode independent of an amount of current drawn by the motor. 
     
     
       14. A method of operating a power tool coupled to a source of electric power and having a motor, a controller, and an input switch, the method comprising:
 determining, in the controller, a position of the input switch that is moveable in a first range of positions between a preset deactivated position and a preset actuated position and in a second range of positions between a first preset intermediate position and the preset deactivated position, the first preset intermediate position between preset deactivated position and the preset actuated position; 
 delivering continuous electric power to the motor when the determined position of the input switch is within the first range of positions, the continuous electric power causing continuous rotation of the motor; and 
 delivering discontinuous electric power to the motor when the determined position of the input switch is within the second range only after being in a position between the first intermediate position and the actuated position, the discontinuous power causing discontinuous rotation of the motor to simulate feathering the input switch. 
 
     
     
       15. The method of  claim 14 , wherein the discontinuous electric power comprises pulses of electrical power with a frequency low enough to be perceptible to a user. 
     
     
       16. The method of  claim 15 , wherein the pulses of electric power comprise pulses of a first power interrupted by pulses of a second power that is different than the first power. 
     
     
       17. The method of  claim 14 , further comprising a second intermediate position of the input switch between the deactivated position and the actuated position, wherein the first range of positions comprises a first subrange of positions between the deactivated position and the second intermediate position and a second subrange of positions between the second intermediate position and the first intermediate position, and wherein delivering continuous electric power comprises delivering a variable amount of electric power when the input switch is within the first subrange of positions, and delivering a constant amount of electric power when the input switch is within the second subrange of positions. 
     
     
       18. The method of  claim 14 , further comprising transitioning from delivering continuous electric power to the motor to delivering discontinuous electric power to the motor, independent of an amount of current drawn by the motor.